Just a thought...
But a Communist Spain - interesting. Wouldn't it be possible that instead of a Vichy France, there'd have been a "French Socialist Republic of Vichy" - or some form of Spanish "Liberation" of portions of France in 1940? Hitler wasn't averse to giving out treats to countries helping him chop up others - Poland, Hungary, and Lithuania got chunks of Czech territory, the USSR got hug gobbets of Poland, Roumania, and the Baltics.
I think it would be an interesting phenomenon to see a Sovietised portion of France. With the huge popularity of the left in France at the time, it might've worked, and been a far better buffer against Hitler than Poland ever was.
IMHO, with Italy's struggles in Greece and Albania, Hitler might well have let Spain have a chunk of France. This might've led to Roumania falling into the Axis sooner, but - IMHO! - would've strengthened the resolve of Bulgaria and Jugoslavija to resist. Who knows, a Soviet France would've helped nab more of the vile Ustashes of Croatia, and beheaded - or at least weakened - the 5th Column there, or at least the information would've given Stalin more leverage with the Jugoslav Crown.